Capacity of Generating Stations
and Weight of Conductors.
| Location of Transmission. | Kilowatt Capacity at Generators. | Total Weight of Conductors. | Pounds of Conductors per Kilowatt Capacity. | |||
|---|---|---|---|---|---|---|
| Wilbraham to Ludlow | 4,600 | 17,820 | 3.7 | [[A]] | ||
| Sewall’s Falls to railroad shops | 50 | 6,914 | 15 | |||
| Into Victor, Colo. | 1,600 | 15,960 | 10 | |||
| To Dales, Ore. | 1,000 | 33,939 | 34 | |||
| Apple River to St. Paul | 3,000 | 159,600 | 53 | |||
| Farmington River to Hartford | 1,500 | 54,054 | 36 | |||
| Cañon City to Cripple Creek | 1,500 | 59,079 | 39 | |||
| Yadkin River to Salem | 1,500 | 58,073 | 39 | |||
| Montmorency Falls to Quebec | 2,400 | 189,056 | 79 | |||
| Cañon Ferry to Butte | 5,700 | 658,320 | 115 | |||
| San Gabriel Cañon to Los Angeles | 1,200 | 73,002 | 61 | |||
| Welland Canal to Hamilton | 6,000 | 376,494 | 63 | |||
| Madrid to Bland, N. M. | 600 | 127,680 | 212 | |||
| Ogden to Salt Lake City | 2,250 | 292,365 | 129 | |||
| Santa Ana River to Los Angeles | 2,250 | 664,830 | 295 | |||
| Colgate to Oakland | 11,250 | - | 906,954 | 81 | ||
| 446,627 | 40 | [[A]] | ||||
| [A] Aluminum. | ||||||
These wide variations in the volts per mile on transmission lines and in length of lines lead to different weights of conductors per kilowatt of generator capacity. All other factors remaining constant, the weight of conductors per kilowatt of generator capacity would be the same whatever the length of the transmission, provided that the volts per mile were uniform for all cases. One important factor, the percentage of loss for which the line conductors are designed at full load, is sure to vary in different cases, and lead to corresponding variations in the weights of conductors per kilowatt of generator capacity. In conductors of equal length one pound of aluminum has nearly the same electrical resistance as two pounds of copper, and this ratio must be allowed for when copper and aluminum lines are compared.
From the table it may be seen that the weight of conductors per kilowatt of generator capacity for the transmission from Santa Ana River is 29.5 times as great as the like weight for the line into Victor. But the volts per mile are four times as great on the Victor as they are on the Santa Ana River line. The extreme range of the cases presented is that between the Ludlow plant, with the equivalent of 7.4 pounds, and the Santa Ana River system with 295 pounds of copper conductors per kilowatt of generator capacity. Three transmissions with 1,575 to 2,555 volts per mile have the equivalent of 7.4 to 15 pounds of copper each, per kilowatt of generator capacity.
Weight and Cost of Conductors.
| Pounds per Kilowatt Mile. | Dollars per Generator Kilowatt. | ||||
|---|---|---|---|---|---|
| Wilbraham to Ludlow | 0 | .86[[A]] | 1.11 | ||
| Sewall’s Falls to railroad shops | 2 | .7 | 2.25 | ||
| Into Victor, Colo. | 0 | .9 | 1.50 | ||
| To Dales, Ore. | 1 | .2 | 5.10 | ||
| Apple River to St. Paul | 2 | .1 | 7.95 | ||
| Farmington River to Hartford | 3 | .2 | 10.80 | ||
| Cañon City to Cripple Creek | 1 | .6 | 5.85 | ||
| Yadkin River to Salem | 2 | .6 | 5.85 | ||
| Montmorency Falls to Quebec | 11 | .2 | 11.85 | ||
| Cañon Ferry to Butte | 1 | .7 | 17.25 | ||
| San Gabriel Cañon to Los Angeles | 2 | .6 | 9.85 | ||
| Welland Canal to Hamilton | 1 | .7 | 9.45 | ||
| Madrid to Bland, N. M. | 6 | .6 | 31.80 | ||
| Ogden to Salt Lake City | 3 | .5 | 19.35 | ||
| Santa Ana River to Los Angeles | 3 | .5 | 44.25 | ||
| Colgate to Oakland | - | .56 | 24.15 | ||
| .27[[A]] | |||||
| [A] Aluminum. | |||||
Of the seven transmissions using between 36 and 79 pounds of copper for each kilowatt of generator capacity, four have voltages ranging from 827 to 1,000 per mile, and on only one is the pressure as low as 643 volts per mile. Five transmission lines vary between 115 and 295 pounds of copper, or its equivalent, per kilowatt of generator capacity, and their voltages per mile are as high as 769 in one case and down to 281 in another. Allowing for some variations in the percentages of loss in transmission lines at full load, the fifteen plants plainly illustrate the advantage of a high voltage per mile, as to the weight of conductors. This advantage is especially clear if the differences due to the lengths of the transmissions are eliminated by dividing the weight of conductors per kilowatt of generator capacity in each case by the length of the transmission in miles. This division gives the weight of conductors per kilowatt of generators for each mile of the line, which may be called the weight per kilowatt mile. For the Ludlow transmission this weight is only 0.86 pound of aluminum, the equivalent of 1.72 pounds of copper, while the like weight for the line into Quebec is 11.2 pounds of copper, or 6.5 times that for the former line. But the voltage per mile on the Ludlow is 3.2 times as great as the like voltage on the Quebec line.
The weight of conductor per kilowatt mile in the Victor line is only 0.9 pound, and the like weight for the line between Madrid and Bland is 6.6 pounds, or 7.3 times as great. On the Victor line the voltage per mile is 2.5 times as great as the voltage for each mile of the Bland line.
Comparing systems with nearly equal voltages per mile, it appears in most cases that only such difference exists in their pounds of conductors per kilowatt mile as may readily be accounted for by designs for various percentages of loss at full load. Though the transmission line into Butte is nearly twice as long as the one entering Hamilton, the weight of conductors for each is 1.7 pounds per kilowatt mile. The line from Santa Ana River is more than twice as long as the one entering Salt Lake City, but its voltage per mile is only nine per cent less, and there are 3.5 pounds of copper in each line per kilowatt mile.